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Police are using sophisticated laser scanning
techniques to create virtual reconstructions of crime scenes - helping
detectives solve difficult cases and juries make more informed decisions.
Jimmy Lee Shreeve reports.
The hugely popular U.S. television show CSI: Crime Scene Investigation
has often been slammed by real life police investigators for being too far
fetched - stretching the facts as well as the science. In truth, investigating
crime scenes is far from glamorous and involves a good deal of painstaking
"plod" work. But it is getting decidedly hi-tech, especially in more complex
cases.
One of the key technologies increasingly being used today by police is laser
scanning, a technique that creates highly accurate 3-D reconstructions of crime
scenes. These reconstructions can be viewed on large plasma computer monitors
and can even be explored from different angles and points-of-view - much as you
can in computer games.
All this is helping detectives crack cases and juries make more informed
decisions. "Understanding evidence documented on a 2-D drawing of a
staircase is difficult. (But) if you create a 3-D staircase and cut-away, the
relevance is often clear," explains laser scanning expert Derry Long of Plowman
Craven and Associates (PCA), a land surveying firm, which also numbers police
authorities amongst its clients.
Long - who spent 12 years as a civilian employee of the Metropolitan Police -
has set up the first hi-tech call-out team in Europe for criminal
investigations. He and his colleagues are on call 24/7 and respond to growing
numbers of incidents every year. Their job involves scanning the area where a
crime has been committed and then recreating it down to sub-millimetre level
using the digital data collected, along with standard photographic documentation
and notes taken from the crime scene.
The kind of detail offered by 3-D laser scanning can make all the difference to
solving the puzzling aspects of a crime. In one particular case, reported in the
U.S. Government Technology magazine, a murder was thought to have
occurred in a kitchen, but no one could work out how the body ended up in the
hallway. By recreating the crime scene virtually, police were able to examine
the area from different points-of-view and work out what happened. Thus gaining
greater insight into crime.
Large scale
Laser scanning is also particularly
useful when a crime has been committed outdoors. Not only does it speed up the
mapping of very large crime scenes, it also enables the investigators to glean
far more detail. When a political execution was committed in a large pasture in
Ireland, investigators used laser scanning to create a virtual map of the scene
and quickly gained vital information they wouldn't otherwise have got using
traditional methods. In the past, the sheer size of the area would have been an
issue and would have involved protracted surveying (using a theodolite),
sketching and photographing.
"The beauty of laser scanning is it can capture enormous scenes down to the
minutest level," says Mark Harrison, MBE, National Police Search Advisor and one
of the officers involved in the investigation in Ireland. Harrison first
used 3-D laser scanning in February 2002 when faced with finding possible
victims after the Yarlswood detention centre for asylum seekers, in
Bedfordshire, burnt down. It was the largest building-based crime scene in
Europe.
"There was concern that bodies might have been in the burnt out building, so a
forensic de-construction of the site had to be performed," he says. "My greatest
difficulty was how to capture the massive crime scene. Because I have close ties
with researchers in both universities and the private sector I was aware of
laser scanning, which was just coming on to the scene."
Minimizing contamination
Another advantage of laser scanning
is it minimises the possibility of crime scene contamination.
"Contamination can take many forms," explains Harrison. "Someone might touch an
object, leaving their fingerprints. Or they might inadvertently move or take
evidence from the scene - possibly by picking up hairs on their shoes. The great
thing about laser scanning is it is non-intrusive. It lets you capture a scene
from a stand-off point-of-view, which greatly reduces the risk of
contamination."
Harrison also points out that scanning a crime scene digitally before anyone
enters is also a way of cementing that scene in stone. When a case comes to
court this can make a big difference to a witness's recollection of events.
"From an evidential perspective it's brilliant because you can pinpoint where
everything was," continues Harrison. "It's also interactive. You can put a
digital representation of a witness into the 3-D model and move them around the
scene. This can help verify what they could or couldn't have seen. It might turn
out, for example, that they couldn't have seen an incident as clearly as they
thought they could because an item of street furniture was in their direct line
of sight."
Laser scanning works equally well in documenting accident scenes. Although not
involved personally, Harrison points out that the technology was used earlier
this year by British police to re-examine the Paris tunnel where Princess Diana
died in a 1997 car crash.
Risk of falsifying evidence
The virtual magic of 3-D laser
scanning is also used to create the stunning visual effects in fantasy movies
such as Tomb Raider and Harry Potter. For some, the fact that
laser scanning technology is used by the entertainment industry to create highly
believable, yet unreal worlds, triggers off alarm bells. "We've got to
embrace these new techniques, but we must clearly understand that the digital
world is an easy one to manipulate," warns Dr David McLay, OBE, of the
Association of Forensic Physicians. "Not only that, but we must ensure that
there is no intentional or even unintentional falsification of the crime scene
and what can be deduced from it."
He also believes it is too easy to be seduced by the lure of new technology:
"Looking at it from the point-of-view of jurisprudence, I would hope there is
always somebody there to challenge this and bring people down to earth a little
bit." Advocates of laser scanning agree that data, by its very nature, can
be tampered with. But insist that what is important during a criminal
investigation is preserving the chain of evidence.
"When laser scanning data is captured it is date stamped and strict protocols
are put in place to ensure integrity and continuity of evidence," explains Tony
Grissom of California-based Leica Geosystems, one of the leading manufacturers
of laser scanning equipment. "While it is conceivable that data could be
tampered with - intelligence agencies like MI5 or the CIA, for example, have the
ability to do pretty much anything - it is an extremely unlikely scenario."
U.S. fragmentation
Although the main thrust of 3-D laser
scanning product development has been in the U.S., the technique is more
commonly used by police forces in Britain. According to Raymond E. Foster, a
retired Los Angeles Police Department (LAPD) lieutenant and author of Police
Technology (Prentice Hall 2004), the main reason for slow take up in the U.S. is
fragmentation. Unlike the U.K., which has 44 police agencies answering to
the home office, we have over 18,000 state and local police agencies answering
to their city, county or state. Getting them on the same page when it comes to
advances in technology is not easy," he says.
Looking back on his time in the LAPD, Foster can recall numerous incidents where
3-D laser scanning technology could have been used to good effect. "I can
think of a ton of homicides where the ability to go back to the scene could have
proved the key to cracking the case."
How does 3-D laser scanning
work?
Three-dimensional laser scanning
systems work by projecting a laser beam across an area. The laser light bounces
off objects and returns to a digital sensor on the scanning device. Laser
scanning essentially measures millions of points at a scene - referred to as the
"point cloud." These are then converted into appropriate digital format and are
used to virtually recreate the area that has been scanned. Any desktop or laptop
computer can take the laser scanned data file and display the material as a 3-D
image that can be explored, much like you can in a computer game.
About Jimmy Lee Shreeve
Jimmy Lee Shreeve is a writer and journalist living in
Britain, but writing for newspapers and magazines around the world. He is
author of a cult bestseller set around hoodoo, blues and rock and roll,
published by St Martin's Press. And is currently writing a true crime title
called "Blood Rites", which investigates the growing numbers of
ritualistic murders, carried out by shamans and religious extremists, that have
occurred in recent years in Africa, South America, and even in England, Ireland
and the USA. Discover more at
www.jimmyleeshreeve.com.
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